This application claims the priority of Korean Patent Application No. 2002-22807 filed on Apr. 25, 2002 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method of and a system for converting color temperatures of visual contents according to a user's preferred color temperature.
2. Description of the Related Art
The color temperature of a light source is defined as the temperature of the planckian radiator, which chromaticity is nearest to that of the source in a suitable uniform chromaticity-scale diagram such as CIE 1960 UCS diagram. The color temperature of an image can be calculated by estimating illumination component of the image. Color Temperature can be used to quantifying the warmness and coolness that a human being feels about the image. In general, an image having a high color temperature is wholly bluish and an image having a low color temperature is wholly reddish. However, individuals' preferred color temperatures are different.
As disclosed in U.S. Pat. Nos. 4,562,460, 4,633,299, and 4,788,586, in the prior arts, in order to convert the color temperature of an image to a user's preferred color temperature, a television or a monitor has an adjusting circuit which can vary the quantity of hue or red, green, blue (RGB) and with which the user can adjust the color temperature of an image or a scene to the user's preferred color temperature.
However, it is very inconvenient for the user to adjust the color temperature each time the user watches a moving picture containing scenes of various contents. Also, in the color temperature converting method, it appears as if converted pictures have passed through a specific color filter. Thus, the displayed pictures look unnatural.
As another color temperature converting method, U.S. Pat. No. 6,172,719 discloses a method of sensing the brightness, color, etc. around a display device and automatically converting the color temperature of the display device using a chromaticity sensing apparatus. In this method, the color temperature is converted according to environmental changes regardless of the characteristics of the picture. Thus, this method is suitable to adjusting a viewer's feelings depending on the environment while being unrelated to the conversion of color temperature according to color temperature characteristics of the visual contents. In general, the environment for watching an image display device, such as a television or a monitor, is constant while the visual contents are inconstant. Thus, when considering that individuals' preferred color temperatures are different, it is necessary to convert the color temperature to correspond to variations in the visual contents.
For this necessity, U.S. Pat. Nos. 4,685,071 and 5,495,428 and Korean Patent Application No.1998-53119 each disclose a method of estimating the color temperature (a luminating color) from an image. Specifically, Korea Patent Application No.1999-50596 discloses a method of simultaneously converting color temperatures of images to a user's preferred color temperatures using estimated color temperatures.
However, these methods have to undergo a color temperature estimating process in which a matrix multiplication operation is performed for each pixel. Thus, when these methods are applied to a user's terminal, a considerable amount of calculation load occurs. As a result, image displaying performance deteriorates, or the cost for improving the image displaying performance increases.